Diels–Kranz numbering

While he was studying the stars and looking upwards, he fell into a pit, and a neat, witty Thracian servant girl jeered at him, they say, because he was so eager to know the things in the sky that he could not see what was there before him at his very feet.

The source is Theaetetus (one of Plato's dialogues), and gives an account of Thales' life, hence it is a testimonium, represented by the letter A.

[5][6][7][8][a] Note that the numbering scheme presented is that of the fifth edition of Die Fragmente der Vorsokratiker, the first to be revised by Kranz.

Although "the Seven Sages of Greece" implies a clearly defined set of seven people, historical disagreement renders intractable the problem of exactly who they were, with multiple sources suggesting several different candidates.

[10] In several cases, the personalities listed are so obscure that they are merely mentioned by name in other sources, commonly with hints as to their geographical and philosophical associations, and without even surviving paraphrases of any of their ideas, or what they might have written.

That is, these more obscure personalities survive in the historical record only as names cited by others, and so came to be included in Diels–Kranz for the sake of scholarly completeness.